1. Field of the Invention
The present invention generally relates to barrier and intrusion detection systems and more particularly, to a novel picket barrier fence system having internally contained intrusion sensing detector devices.
2. Description of the Prior Art
Existing technology in perimeter security systems typically includes the use of various types of fences in combination with barbed obstacles and various types of alarm systems. Such alarm systems utilize electronic sensors to augment the fence barrier and create an alarm if the perimeter is breached. In general, the more sophisticated perimeter systems currently in use combine an aggregate of the above devices, e.g. fence, barbed obstacle and electronic sensor, in order to provide first, a notice of the attempted intrusion, then a delay of the actual intrusion. Little technology exists to combine such devices in what is considered to be an optimal manner. The result is that the physical barrier often diminishes the effectiveness of the sensor or vice versa.
Prior art attempts to solve the problem are disclosed in U.S. Pat. Nos. 4,097,025 to Dettmann et al; 4,155,083 to Slaats et al.; and 4,197,529 to Ramstedt et al. In the Detmann et al. patent, vibration sensors are connected to a fence so as to generate signals for input to an alarm system in the event that one attempts to violate the fence and in so doing causes vibration that can be sensed. Slaats discloses a fence made of wire elements comprised of coaxial conductive layers separated by a thin insulated layer. Intruder pressure applied to the fence generates a contact resistance between the conductive layers or a change in capacitance between that layers that results in a measurable event which upon detection causes an alarm system to be actuated.
A time domain reflectometer is utilized by Ramstedt et al. in combination with an external conductive sheath and an internal conductor separated by a layer of insulating material such that any deformation of the sheath relative to the central conductor generates a variation in the impedance of the cable which can be detected and used to actuate an alarm.
Each of the above prior art approaches are subject to the disadvantages of either requiring aesthetically unpleasing fence structures or apparatus which can be easily violated by knowledgeable and patient intruders.